Systems that manipulate analog, digital, or mixed signals generally use a reference potential for a variety of operations. For example, a conventional analog-to-digital converter (ADC) system usually includes a reference circuit, relying on a reference potential, to establish a range for signal conversion. The reference potential should be reproducible to provide consistent performance.
One manner of obtaining the reference potential is with a reference based on the bandgap energy of a semiconductor material. By applying a reference current to two diodes or p-n junction devices having different diode areas and measuring the voltage drops across such devices, the bandgap energy of the diode semiconductor (e.g., silicon) may be determined. The measured bandgap energy is generally a physical constant, although the bandgap energy may drift in response to temperature. This measurement is typically performed in the analog domain and may be inaccurate due to device mismatch (e.g., non-ideal devices or devices having non-uniform properties as a result of the manufacturing process thereof). For example, variations in the circuits supplying the reference currents to the diodes and device mismatch can cause as much as a five-percent (5%) variation in the reference potential determination.
Accordingly, a method and a circuit for producing a reference signal having improved accuracy are desired. In addition, a method and a circuit for producing a reference signal having improved accuracy and that can be used with a varying reference are desired. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.